Formosa Plastics Group's steel plant in Vietnam restarted on Monday after its operations were halted for causing one of the country's worst environmental disasters, local media reported.

In April last year, the $11 billion Formosa Ha Tinh Steel plant accidentally spilled toxic waste that polluted more than 200 km (125 miles) of coastline, devastating sea life and local economies dependent on fishing and tourism. Taiwanese-owned Formosa paid $500 million in compensation.

Formosa has met requirements to test-run its first blast furnace, local media quoted Deputy Environment Minister Nguyen Linh Ngoc as saying.

Authorities will closely monitor the furnace and the initial result of the run will be available in 24 hours, while waste samples will be taken every five minutes, local media quoted senior environmental official Hoang Duong Tung as saying.

Formosa has addressed 52 out of 53 violations identified, Tung said, adding the company was expected to put in place a dry coking system by 2019 to replace the current wet coking system, which is cheaper but dirtier.

Formosa in March said it would boost investment by about $350 million in the project to improve environmental safety measures with the hope of starting commercial production by the fourth quarter of this year.